Designation: C 94/C 94M – 04
Standard Specification for
Ready-Mixed Concrete1
This standard is issued under the fixed designation C 94/C 94M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
lindrical Concrete Specimens
C 109/C 109M Test Method for Compressive Strength of
Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube
Specimens)
C 138/C 138M Test Method for Density (Unit Weight),
Yield, and Air Content (Gravimetric) of Concrete
C 143/C 143M Test Method for Slump of Hydraulic Cement Concrete
C 150 Specification for Portland Cement
C 172 Practice for Sampling Freshly Mixed Concrete
C 173/C 173M Test Method for Air Content of Freshly
Mixed Concrete by the Volumetric Method
C 191 Test Method for Time of Setting of Hydraulic Cement by Vicat Needle
C 231 Test Method for Air Content of Freshly Mixed
Concrete by the Pressure Method
C 260 Specification for Air-Entraining Admixtures for Concrete
C 330 Specification for Lightweight Aggregates for Structural Concrete
C 494/C 494M Specification for Chemical Admixtures for
Concrete
C 567 Test Method for Determining Density of Structural
Lightweight Concrete
C 595 Specification for Blended Hydraulic Cements
C 618 Specification for Coal Fly Ash and Raw or Calcined
Natural Pozzolan for Use as a Mineral Admixture in
Concrete
C 637 Specification for Aggregates for Radiation-Shielding
Concrete
C 989 Specification for Ground Granulated Blast-Furnace
Slag for Use in Concrete and Mortars
C 1017/C 1017M Specification for Chemical Admixtures
for Use in Producing Flowing Concrete
C 1064/C 1064M Test Method for Temperature of Freshly
Mixed Portland-Cement Concrete
C 1077 Practice for Laboratories Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for
Laboratory Evaluation
C 1157 Performance Specification for Hydraulic Cement
D 512 Test Methods for Chloride Ion in Water
1. Scope
1.1 This specification covers ready-mixed concrete manufactured and delivered to a purchaser in a freshly mixed and
unhardened state as hereinafter specified. Requirements for
quality of concrete shall be either as hereinafter specified or as
specified by the purchaser. In any case where the requirements
of the purchaser differ from these in this specification, the
purchaser’s specification shall govern. This specification does
not cover the placement, consolidation, curing, or protection of
the concrete after delivery to the purchaser.
1.2 The values stated in either SI units, shown in brackets,
or inch-pound units are to be regarded separately as standard.
The values stated in each system may not be exact equivalents;
therefore, each system shall be used independently of the other.
Combining values from the two systems may result in nonconformance with the standard.
1.3 As used throughout this specification the manufacturer
shall be the contractor, subcontractor, supplier, or producer
who furnishes the ready-mixed concrete. The purchaser shall
be the owner or representative thereof.
1.4 The text of this standard references notes and footnotes
which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered
as requirements of the standard.
2. Referenced Documents
2.1 ASTM Standards: 2
C 31/C 31M Practice for Making and Curing Concrete Test
Specimens in the Field
C 33 Specification for Concrete Aggregates
C 39/C 39M Test Method for Compressive Strength of Cy-
1
This specification is under the jurisdiction of ASTM Committee C09 on
Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee
C09.40 on Ready-Mixed Concrete.
Current edition approved Feb. 1, 2004. Published March 2004. Originally
approved in 1933. Last previous edition approved in 2003 as C 94/C 94M–03e1.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C 94/C 94M – 04
TABLE 1 Recommended Total Air Content for Air-Entrained ConcreteA,B
Exposure
ConditionC
Mild
Moderate
Severe
⁄ [9.5]
4.5
6.0
7.5
38
⁄ [12.5]
4.0
5.5
7.0
12
Total Air Content, %
Nominal Maximum Sizes of Aggregate, in. [mm]
⁄ [19.0]
1 [25.0]
11⁄2 [37.5]
3.5
3.0
2.5
5.0
4.5
4.5
6.0
6.0
5.5
34
2 [50.0]
2.0
4.0
5.0
3 [75.0]
1.5
3.5
4.5
A
For air-entrained concrete, when specified.
Unless exposure conditions dictate otherwise, it is permissible to reduce air contents recommended above by up to 1 % for concretes with specified compressive
strength, f8c, of 5000 psi [35 MPa] or above.
C
For description of exposure conditions, refer to Standard Practice ACI 211.1, Section 6.3.3, with attention to accompanying footnotes.
B
4.1.1 Designated size, or sizes, of coarse aggregate,
4.1.2 Slump, or slumps, desired at the point of delivery (see
Section 6 for acceptable tolerances),
4.1.3 When air-entrained concrete is specified, the air content of the samples taken at the point of discharge from the
transportation unit (see Section 7 and Table 1 for the total air
content and tolerances) (Note 2),
4.1.4 Which of Options A, B, or C shall be used as a basis
for determining the proportions of the concrete to produce the
required quality, and
4.1.5 When structural lightweight concrete is specified, the
mass per unit volume as wet mass, air-dry mass, or oven-dry
mass (Note 3).
D 516 Test Method for Sulfate Ion in Water
2.2 ACI Documents:3
CP-1 Technician Workbook for ACI Certification of Concrete Field Testing Technician–Grade I
211.1 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete
211.2 Standard Practice for Selecting Proportions for Structural Lightweight Concrete
301 Standard Specifications for Structural Concrete
305R Hot Weather Concreting
306R Cold Weather Concreting
318 Building Code Requirements for Structural Concrete
and Commentary
2.3 Other Documents:
Bureau of Reclamation Concrete Manual4
AASHTO T26 Method of Test for Quality of Water to be
Used in Concrete5
NOTE 2—In selecting the specified air content, the purchaser should
consider the exposure conditions to which the concrete will be subjected.
Air contents less than shown in Table 1 may not give the required
resistance to freezing and thawing, which is the primary purpose of
air-entrained concrete. Air contents higher than the levels shown may
reduce strength without contributing any further improvement of durability.
NOTE 3—The mass per unit volume of fresh concrete, which is the only
unit mass determinable at the time of delivery, is always higher than the
air-dry or oven-dry mass. Definitions of, and methods for determining or
calculating air-dry and oven-dry masses, are covered by Test Method
C 567.
3. Basis of Purchase
3.1 The basis of purchase shall be the cubic yard or cubic
metre of freshly mixed and unhardened concrete as discharged
from the mixer.
3.2 The volume of freshly mixed and unhardened concrete
in a given batch shall be determined from the total mass of the
batch divided by the mass per unit volume of the concrete. The
total mass of the batch shall be calculated either as the sum of
the masses of all materials, including water, entering the batch
or as the net mass of the concrete in the batch as delivered. The
mass per unit volume shall be determined in accordance with
Test Method C 138/C 138M from the average of at least three
measurements, each on a different sample using a 1⁄2-ft3 [14-L3]
container. Each sample shall be taken from the midpoint of
each of three different truck loads by the procedure outlined in
Practice C 172.
4.2 Option A:
4.2.1 When the purchaser requires the manufacturer to
assume full responsibility for the selection of the proportions
for the concrete mixture (Note 4), the purchaser shall also
specify the following:
4.2.1.1 Requirements for compressive strength as determined on samples taken from the transportation unit at the
point of discharge evaluated in accordance with Section 17.
The purchaser shall specify the requirements in terms of the
compressive strength of standard specimens cured under standard laboratory conditions for moist curing (see Section 17).
Unless otherwise specified the age at test shall be 28 days.
NOTE 1—It should be understood that the volume of hardened concrete
may be, or appear to be, less than expected due to waste and spillage,
over-excavation, spreading forms, some loss of entrained air, or settlement
of wet mixtures, none of which are the responsibility of the producer.
NOTE 4—The purchaser, in selecting requirements for which he assumes responsibility should give consideration to requirements for workability, placeability, durability, surface texture, and density, in addition to
those for structural design. The purchaser is referred to Standard Practice
ACI 211.1 and Standard Practice ACI 211.2 for the selection of proportions that will result in concrete suitable for various types of structures and
conditions of exposure. The water-cement ratio of most structural lightweight concretes cannot be determined with sufficient accuracy for use as
a specification basis.
4. Ordering Information
4.1 In the absence of designated applicable general specifications, the purchaser shall specify the following:
3
Available from American Concrete Institute, 38800 Country Club Drive,
Farmington Hills, MI 48331.
4
Available from Superintendent of Documents, U. S. Government Printing
Office, Washington, DC 20402.
5
Available from the American Association of State Highway and Transportation
Officials, 444 N. Capitol St., NW, Suite 225, Washington, DC 20001.
4.2.2 At the request of the purchaser, the manufacturer shall,
prior to the actual delivery of the concrete, furnish a statement
to the purchaser, giving the dry masses of cement and saturated
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C 94/C 94M – 04
surface-dry masses of fine and coarse aggregate and quantities,
type, and name of admixture (if any) and of water per cubic
yard or cubic metre of concrete that will be used in the
manufacture of each class of concrete ordered by the purchaser.
He shall also furnish evidence satisfactory to the purchaser that
the materials to be used and proportions selected will produce
concrete of the quality specified. Whatever strengths are
attained the quantity of cement used shall not be less than the
minimum specified.
4.5 The proportions arrived at by Options A, B, or C for
each class of concrete and approved for use in a project shall
be assigned a designation to facilitate identification of each
concrete mixture delivered to the project. This is the designation required in 13.1.7 and supplies information on concrete
proportions when they are not given separately on each
delivery ticket as outlined in 13.2. A certified copy of all
proportions as established in Options A, B, or C shall be on file
at the batch plant.
4.6 The purchaser shall ensure that the manufacturer is
provided copies of all reports of tests performed on concrete
samples taken to determine compliance with specification
requirements. Reports shall be provided on a timely basis.
surface-dry-masses of fine and coarse aggregate and quantities,
type, and name of admixtures (if any) and of water per cubic
yard or cubic metre of concrete that will be used in the
manufacture of each class of concrete ordered by the purchaser.
He shall also furnish evidence satisfactory to the purchaser that
the materials to be used and proportions selected will produce
concrete of the quality specified.
4.3 Option B:
4.3.1 When the purchaser assumes responsibility for the
proportioning of the concrete mixture, he shall also specify the
following:
4.3.1.1 Cement content in bags or pounds per cubic yard
[kilograms per cubic metre] of concrete,
4.3.1.2 Maximum allowable water content in gallons per
cubic yard [litres per cubic metre] of concrete, including
surface moisture on the aggregates, but excluding water of
absorption (Note 4), and
4.3.1.3 If admixtures are required, the type, name, and
dosage to be used. The cement content shall not be reduced
when admixtures are used under this option without the written
approval of the purchaser.
4.3.2 At the request of the purchaser, the manufacturer shall,
prior to the actual delivery of the concrete, furnish a statement
to the purchaser giving the sources, densities, and sieve
analyses of the aggregates and the dry masses of cement and
saturated-surface-dry masses of fine and coarse aggregate and
quantities, type and name of admixture (if any) and of water
per cubic yard or cubic metre of concrete that will be used in
the manufacture of each class of concrete ordered by the
purchaser.
4.4 Option C:
4.4.1 When the purchaser requires the manufacturer to
assume responsibility for the selection of the proportions for
the concrete mixture with the minimum allowable cement
content specified (Note 5), the purchaser shall also specify the
following:
4.4.1.1 Required compressive strength as determined on
samples taken from the transportation unit at the point of
discharge evaluated in accordance with Section 17. The purchaser shall specify the requirements for strength in terms of
tests of standard specimens cured under standard laboratory
conditions for moist curing (see Section 17). Unless otherwise
specified the age at test shall be 28 days.
4.4.1.2 Minimum cement content in bags or pounds per
cubic yard [kilograms per cubic metre] of concrete.
4.4.1.3 If admixtures are required, the type, name, and
dosage to be used. The cement content shall not be reduced
when admixtures are used.
5. Materials
5.1 In the absence of designated applicable specifications
covering requirements for quality of materials, the following
specifications shall govern:
5.1.1 Cement—Cement shall conform to Specification
C 150, Specification C 595, or Specification C 1157 (see Note
6). The purchaser shall specify the type or types required, but
if no type is specified, the requirements of Type I as prescribed
in Specification C 150 shall apply.
NOTE 6—These different cements will produce concretes of different
properties and should not be used interchangeably.
5.1.2 Aggregates—Normal weight aggregates shall conform
to Specification C 33. Lightweight aggregates shall conform to
Specification C 330 and heavyweight aggregates shall conform
to Specification C 637.
5.1.3 Water:
5.1.3.1 The mixing water shall be clear and apparently
clean. If it contains quantities of substances which discolor it or
make it smell or taste unusual or objectionable or cause
suspicion, it shall not be used unless service records of
concrete made with it or other information indicates that it is
not injurious to the quality of the concrete. Water of questionable quality shall be subject to the acceptance criteria of Table
2.
5.1.3.2 Wash water from mixer washout operations is permitted to be used for mixing concrete provided tests of wash
water comply with the physical test limits of Table 2. Wash
water shall be tested at a weekly interval for approximately 4
weeks, and thereafter at a monthly interval provided no single
test exceeds the applicable limit (Note 7). Optional chemical
limits in Table 3 shall be specified by the purchaser when
appropriate for the construction. The testing frequency for
chemical limits shall be as given above or as specified by the
purchaser.
NOTE 5—Option C can be distinctive and useful only if the designated
minimum cement content is at about the same level that would ordinarily
be required for the strength, aggregate size, and slump specified. At the
same time, it must be an amount that will be sufficient to ensure durability
under expected service conditions, as well as satisfactory surface texture
and density, in the event specified strength is attained with it. For
additional information refer to Standard Practice ACI 211.1 and Standard
Practice 211.2 referred to in Note 4.
4.4.2 At the request of the purchaser, the manufacturer shall,
prior to the actual delivery of the concrete, furnish a statement
to the purchaser, giving the dry masses of cement and saturated
NOTE 7—When recycled wash water is used, attention should be given
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C 94/C 94M – 04
TABLE 2 Acceptance Criteria for Questionable Water Supplies
Limits
90
from 1:00 early
to 1:30 later
Compressive strength, min % control at 7 days
Time of set, deviation from control, h: min
A
Test Method
C 109/C 109MA
C 191A
Comparisons shall be based on fixed proportions and the same volume of test water compared to control mix using city water or distilled water.
TABLE 3 Optional Chemical Limits for Wash Water
Limits
Chemical requirements, maximum concentration in mixing
water, ppmB
Chloride as Cl, ppm:
Prestressed concrete or in bridge decks
Other reinforced concrete in moist environments or
containing aluminum embedments or dissimilar metals
or with stay-in-place galvanized metal forms
Sulfate as SO4, ppm
Alkalies as (Na2O + 0.658 K2O), ppm
Total solids, ppm
Test MethodA
D 512
500C
1000C
3000
600
50 000
D 516
AASHTO T26
A
Other test methods that have been demonstrated to yield comparable results are permitted to be used.
B
Wash water reused as mixing water in concrete is allowed to exceed the listed concentrations if it can be shown that the concentration calculated in the total mixing
water, including mixing water on the aggregates and other sources does not exceed the stated limits.
C
For conditions allowing use of CaCl2 accelerator as an admixture, the chloride limitation is permitted to be waived by the purchaser.
to effects on the dosage rate and batching sequence of air-entraining and
other chemical admixtures, and a uniform amount should be used in
consecutive batches.
2 in. [50 mm] and less
More than 2 through 4 in. [50 to 100 mm]
More than 4 in. [100 mm]
5.1.4 Mineral Admixtures—Coal fly ash and raw or calcined
natural pozzolan shall conform to Specification C 618 as
applicable.
5.1.5 Ground Granulated Blast-Furnace Slag—Ground
granulated blast- furnace slag shall conform to Specification
C 989.
5.1.6 Air-Entraining Admixtures—Air-entraining admixtures shall conform to Specification C 260 (Note 8).
5.1.7 Chemical Admixtures—Chemical admixtures shall
conform to either Specification C 494/C 494M or C 1017/
C 1017M as applicable (Note 8).
6.2 Concrete shall be available within the permissible range
of slump for a period of 30 min starting either on arrival at the
job site or after the initial slump adjustment permitted in 11.7,
whichever is later. The first and last 1⁄4 yd3 or 1⁄4 m3 discharged
are exempt from this requirement. If the user is unprepared for
discharge of the concrete from the vehicle, the producer shall
not be responsible for the limitation of minimum slump after
30 min have elapsed starting either on arrival of the vehicle at
the prescribed destination or at the requested delivery time,
whichever is later.
7. Air-Entrained Concrete
7.1 When air-entrained concrete is desired the purchaser
shall specify the total air content of the concrete. See Table 1
for recommended total air contents (Note 8).
7.2 The air content of air-entrained concrete when sampled
from the transportation unit at the point of discharge shall be
within a tolerance of 6 1.5 of the specified value.
7.3 When a preliminary sample taken within the time limits
of 11.7 and prior to discharge for placement shows an air
content below the specified level by more than the allowable
tolerance in accordance with 7.2, the manufacturer may use
additional air entraining admixture to achieve the desired air
content level, followed by a minimum of 30 revolutions at
mixing speed, so long as the revolution limit of 11.7 is not
exceeded (see Note 9).
NOTE 8—In any given instance, the required dosage of air-entraining,
accelerating, and retarding admixtures may vary. Therefore, a range of
dosages should be allowed which will permit obtaining the desired effect.
6. Tolerances in Slump
6.1 Unless other tolerances are included in the project
specifications, the following shall apply.
6.1.1 When the project specifications for slump are written
as a “maximum” or “not to exceed” requirement:
Specified slump:
If 3 in. [75 mm]
or less
0
11⁄2 in. [40 mm]
Plus tolerance:
Minus tolerance:
If more than 3 in.
[75 mm]
0
21⁄2 in. [65 mm]
This option is to be used only if one addition of water is
permitted on the job provided such addition does not increase
the water-cement ratio above the maximum permitted by the
specifications.
6.1.2 When the project specifications for slump are not
written as a “maximum” or “not to exceed” requirement:
NOTE 9—Acceptance sampling and testing in accordance with Practice
C 172 is not obviated by this provision.
8. Measuring Materials
8.1 Except as otherwise specifically permitted, cement shall
be measured by mass. When mineral admixtures (including
ground granulated blast-furnace slag, coal fly ash, silica fume,
or other pozzolans) are specified in the concrete proportions,
the cumulative mass is permitted to be measured with cement,
Tolerances for Nominal Slumps
For Specified Slump of:
61⁄2 in. [15 mm]
61 in. [25 mm]
611⁄2 in. [40 mm]
Tolerance
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C 94/C 94M – 04
designed and operated so as to discharge efficiently and freely,
with minimum segregation, into the weighing hopper. Means
of control shall be provided so that, as the quantity desired in
the weighing hopper is approached, the material shall be shut
off with precision. Weighing hoppers shall be constructed so as
to eliminate accumulations of tare materials and to discharge
fully.
9.2 Indicating devices shall be in full view and near enough
to be read accurately by the operator while charging the hopper.
The operator shall have convenient access to all controls.
9.3 Scales shall be considered accurate when at least one
static load test within each quarter of the scale capacity can be
shown to be within 60.2 % of the total capacity of the scale.
9.4 Adequate standard test weights shall be available for
checking accuracy. All exposed fulcrums, clevises, and similar
working parts of scales shall be kept clean. Beam scales shall
be equipped with a balance indicator sensitive enough to show
movement when a weight equal to 0.1 % of the nominal
capacity of the scale is placed in the batch hopper. Pointer
travel shall be a minimum of 5 % of the net-rated capacity of
the largest weigh beam for underweight and 4 % for overweight.
9.5 The device for the measurement of the added water shall
be capable of delivering to the batch the quantity required
within the accuracy required in 8.3. The device shall be so
arranged that the measurements will not be affected by variable
pressures in the water supply line. Measuring tanks shall be
equipped with outside taps and valves to provide for checking
their calibration unless other means are provided for readily
and accurately determining the amount of water in the tank.
but in a batch hopper and on a scale which is separate and
distinct from those used for other materials. The mass of the
cement shall be measured before mineral admixtures. When
the quantity of cement exceeds 30 % of the full capacity of the
scale, the quantity of the cement shall be within6 1 % of the
required mass, and the cumulative quantity of cement plus
mineral admixtures shall also be within 61 % of the required
mass. For smaller batches to a minimum of 1 yd3 [1 m3], the
quantity of the cement and the cumulative quantity of cement
plus mineral admixture used shall be not less than the required
amount nor more than 4 % in excess. Under special circumstances approved by the purchaser, cement is permitted to be
measured in bags of standard mass (Note 10). No fraction of a
bag of cement shall be used unless its mass has been determined.
NOTE 10—In the United States the standard mass of a bag of portland
cement is 94 lb [42.6 kg] 63 %.
8.2 Aggregate shall be measured by mass. Batch mass
measurements shall be based on dry materials and shall be the
required masses of dry materials plus the total mass of moisture
(both absorbed and surface) contained in the aggregate. The
quantity of aggregate used in any batch of concrete as indicated
by the scale shall be within 62 % of the required mass when
the mass is measured in individual aggregate weigh batchers.
In a cumulative aggregate weigh batcher, the cumulative
weight after each successive weighing shall be within 61 % of
the required cumulative amount up to that point when the scale
is used in excess of 30 % of its capacity. For cumulative
weights for less than 30 % of scale capacity, the tolerance shall
be 60.3 % of scale capacity or 63 % of the required cumulative weight, whichever is less.
8.3 Mixing water shall consist of water added to the batch,
ice added to the batch, water occurring as surface moisture on
the aggregates, and water introduced in the form of admixtures.
The added water shall be measured by weight or volume to an
accuracy of 1 % of the required total mixing water. Added ice
shall be measured by weight. In the case of truck mixers, any
wash water retained in the drum for use in the next batch of
concrete shall be accurately measured; if this proves impractical or impossible the wash water shall be discharged prior to
loading the next batch of concrete. Total water (including any
wash water) shall be measured or weighed to an accuracy of
63 % of the specified total amount.
8.4 Admixtures in powdered form shall be measured by
mass. Liquid admixtures shall be batched by mass or volume.
Admixtures, except mineral admixtures (see 8.1), measured by
either mass or volume, shall be batched with an accuracy of
63 % of the total amount required or plus or minus the amount
or dosage required for 100 lb [50 kg] of cement, whichever is
greater.
NOTE 12—The scale accuracy limitations of the National Ready Mixed
Concrete Association Plant Certification meet the requirements of this
specification.
10. Mixers and Agitators
10.1 Mixers will be stationary mixers or truck mixers.
Agitators will be truck mixers or truck agitators.
10.1.1 Stationary mixers shall be equipped with a metal
plate or plates on which are plainly marked the mixing speed
of the drum or paddles, and the maximum capacity in terms of
the volume of mixed concrete. When used for the complete
mixing of concrete, stationary mixers shall be equipped with an
acceptable timing device that will not permit the batch to be
discharged until the specified mixing time has elapsed.
10.1.2 Each truck mixer or agitator shall have attached
thereto in a prominent place a metal plate or plates on which
are plainly marked the gross volume of the drum, the capacity
of the drum or container in terms of the volume of mixed
concrete, and the minimum and maximum mixing speeds of
rotation of the drum, blades, or paddles. When the concrete is
truck mixed as described in 11.5, or shrink mixed as described
in 11.4, the volume of mixed concrete shall not exceed 63 % of
the total volume of the drum or container. When the concrete
is central mixed as described in 11.3, the volume of concrete in
the truck mixer or agitator shall not exceed 80 % of the total
volume of the drum or container. Truck mixers and agitators
shall be equipped with means to readily verify the number of
revolutions of the drum, blades, or paddles.
NOTE 11—Admixture dispensers of the mechanical type capable of
adjustment for variation of dosage, and of simple calibration, are
recommended.
9. Batching Plant
9.1 Bins with adequate separate compartments shall be
provided in the batching plant for fine and for each required
size of coarse aggregate. Each bin compartment shall be
5
C 94/C 94M – 04
11.3.1 Where no mixer performance tests are made, the
acceptable mixing time for mixers having capacities of 1 yd3
[0.76 m3] or less shall be not less than 1 min. For mixers of
greater capacity, this minimum shall be increased 15 s for each
cubic yard [cubic metre] or fraction thereof of additional
capacity.
11.3.2 Where mixer performance tests have been made on
given concrete mixtures in accordance with the testing program
set forth in the following paragraphs, and the mixers have been
charged to their rated capacity, the acceptable mixing time is
permitted to be reduced for those particular circumstances to a
point at which satisfactory mixing defined in 11.3.3 shall have
been accomplished. When the mixing time is so reduced the
maximum time of mixing shall not exceed this reduced time by
more than 60 s for air-entrained concrete.
11.3.3 Sampling for Uniformity Tests of Stationary
Mixers—Samples of concrete for comparative purposes shall
be obtained immediately after arbitrarily designated mixing
times, in accordance with one of the following procedures:
11.3.3.1 Alternative Procedure 1—The mixer shall be
stopped, and the required samples removed by any suitable
means from the concrete at approximately equal distances from
the front and back of the drum, or
11.3.3.2 Alternative Procedure 2—As the mixer is being
emptied, individual samples shall be taken after discharge of
approximately 15 % and 85 % of the load. The method of
sampling shall provide that the samples are representative of
widely separated portions, but not from the very ends of the
batch (Note 14).
11.3.3.3 The samples of concrete shall be tested in accordance with Section 17, and differences in test results for the
two samples shall not exceed those given in Annex A1. Mixer
performance tests shall be repeated whenever the appearance
of the concrete or the coarse aggregate content of samples
selected as outlined in this section indicates that adequate
mixing has not been accomplished.
11.4 Shrink-Mixed Concrete—Concrete that is first partially
mixed in a stationary mixer, and then mixed completely in a
truck mixer, shall conform to the following: The time of partial
mixing shall be minimum required to intermingle the ingredients. After transfer to a truck mixer the amount of mixing at the
designated mixing speed will be that necessary to meet the
requirements for uniformity of concrete as indicated in Annex
A1. Tests to confirm such performance shall be made in
accordance with 11.3.3 and 11.3.3.3. Additional turning of the
mixer, if any, shall be at a designated agitating speed.
11.5 Truck-Mixed Concrete—Concrete that is completely
mixed in a truck mixer, 70 to 100 revolutions at the mixing
speed designated by the manufacturer to produce the uniformity of concrete indicated in Annex A1. Concrete uniformity
tests shall be made in accordance with 11.5.1 and if requirements for uniformity of concrete indicated in Annex A1 are not
met with 100 revolutions of mixing, after all ingredients
including water, are in the drum, that mixer shall not be used
until the condition is corrected, except as provided in 10.5.
When satisfactory performance is found in one truck mixer, the
performance of mixers of substantially the same design and
condition of blades are permitted to be regarded as satisfactory.
10.2 All stationary and truck mixers shall be capable of
combining the ingredients of the concrete within the specified
time or the number of revolutions specified in 10.5, into a
thoroughly mixed and uniform mass and of discharging the
concrete so that not less than five of the six requirements
shown in Table A1.1 shall have been met.
NOTE 13—The sequence or method of charging the mixer will have an
important effect on the uniformity of the concrete.
10.3 The agitator shall be capable of maintaining the mixed
concrete in a thoroughly mixed and uniform mass and of
discharging the concrete with a satisfactory degree of uniformity as defined by Annex A1.
10.4 Slump tests of individual samples taken after discharge
of approximately 15 % and 85 % of the load will provide a
quick check of the probable degree of uniformity (Note 14).
These two samples shall be obtained within an elapsed time of
not more than 15 min. If these slumps differ more than that
specified in Annex A1, the mixer or agitator shall not be used
unless the condition is corrected, except as provided in 10.5.
NOTE 14—No samples should be taken before 10 % or after 90 % of the
batch has been discharged. Due to the difficulty of determining the actual
quantity of concrete discharged, the intent is to provide samples that are
representative of widely separated portions, but not the beginning and end
of the load.
10.5 Use of the equipment is permitted when operation with
a longer mixing time, a smaller load, or a more efficient
charging sequence will permit the requirements of Annex A1 to
be met.
10.6 Mixers and agitators shall be examined or their mass
determined as frequently as necessary to detect changes in
condition due to accumulations of hardened concrete or mortar
and examined to detect wear of blades. When such changes are
extensive enough to affect the mixer performance, the prooftests described in Annex A1 shall be performed to show
whether the correction of deficiencies is required.
11. Mixing and Delivery
11.1 Ready-mixed concrete shall be mixed and delivered to
the point designated by the purchaser by means of one of the
following combinations of operations:
11.1.1 Central-Mixed Concrete.
11.1.2 Shrink-Mixed Concrete.
11.1.3 Truck-Mixed Concrete.
11.2 Mixers and agitators shall be operated within the limits
of capacity and speed of rotation designated by the manufacturer of the equipment.
11.3 Central-Mixed Concrete—Concrete that is mixed completely in a stationary mixer and transported to the point of
delivery either in a truck agitator, or a truck mixer operating at
agitating speed, or in nonagitating equipment approved by the
purchaser and meeting the requirements of Section 12, shall
conform to the following: The mixing time shall be counted
from the time all the solid materials are in the drum. The batch
shall be so charged into the mixer that some water will enter in
advance of the cement and aggregate, and all water shall be in
the drum by the end of the first one fourth of the specified
mixing time.
6
C 94/C 94M – 04
Additional revolutions of the mixer beyond the number found
to produce the required uniformity of concrete shall be at a
designated agitating speed.
11.5.1 Sampling for Uniformity of Concrete Produced in
Truck Mixers—The concrete shall be discharged at the normal
operating rate for the mixer being tested, with care being
exercised not to obstruct or retard the discharge by an incompletely opened gate or seal. Separate samples, each consisting
of approximately 2 ft3 [0.1 m3 approximately] shall be taken
after discharge of approximately 15 % and 85 % of the load
(Note 14). These samples shall be obtained within an elapsed
time of not more than 15 min. The samples shall be secured in
accordance with Practice C 172, but shall be kept separate to
represent specific points in the batch rather than combined to
form a composite sample. Between samples, where necessary
to maintain slump, the mixer shall be turned in mixing
direction at agitating speed. During sampling the receptacle
shall receive the full discharge of the chute. Sufficient personnel must be available to perform the required tests promptly.
Segregation during sampling and handling must be avoided.
Each sample shall be remixed the minimum amount to ensure
uniformity before specimens are molded for a particular test.
11.6 When a truck mixer or truck agitator is used for
transporting concrete that has been completely mixed in a
stationary mixer, any turning during transportation shall be at
the speed designated by the manufacturer of the equipment as
agitating speed.
11.7 When a truck mixer or agitator is approved for mixing
or delivery of concrete, no water from the truck water system
or elsewhere shall be added after the initial introduction of
mixing water for the batch except when on arrival at the job
site the slump of the concrete is less than that specified. Such
additional water to bring the slump within required limits shall
be injected into the mixer under such pressure and direction of
flow that the requirements for uniformity specified in Annex
A1 are met. The drum or blades shall be turned an additional
30 revolutions or more if necessary, at mixing speed, until the
uniformity of the concrete is within these limits. Water shall
not be added to the batch at any later time. Discharge of the
concrete shall be completed within 11⁄2 h, or before the drum
has revolved 300 revolutions, whichever comes first, after the
introduction of the mixing water to the cement and aggregates
or the introduction of the cement to the aggregates. These
limitations are permitted to be waived by the purchaser if the
concrete is of such slump after the 11⁄2-h time or 300-revolution
limit has been reached that it can be placed, without the
addition of water, to the batch. In hot weather, or under
conditions contributing to quick stiffening of the concrete, a
time less than 11⁄2 h is permitted to be specified by the
purchaser.
11.8 Concrete delivered in cold weather shall have the
applicable minimum temperature indicated in the following
table. (The purchaser shall inform the producer as to the type
of construction for which the concrete is intended.)
12–36 [300–900]
36–72 [900–1800]
>72 [>1800]
The maximum temperature of concrete produced with
heated aggregates, heated water, or both, shall at no time
during its production or transportation exceed 90°F [32°C].
NOTE 15—When hot water is used rapid stiffening may occur if hot
water is brought in direct contact with the cement. Additional information
on cold weather concreting is contained in ACI 306R.
11.9 The producer shall deliver the ready mixed concrete
during hot weather at concrete temperatures as low as practicable, subject to the approval of the purchaser.
NOTE 16—In some situations difficulty may be encountered when
concrete temperatures approach 90°F [32°C]. Additional information may
be found in the Bureau of Reclamation Concrete Manual and in ACI
305R.
12. Use of Nonagitating Equipment
12.1 When the use of non-agitating transportation equipment is approved by the purchaser, the concrete shall be
manufactured in a central mix plant. The proportions of the
concrete shall be approved by the purchaser and the following
limitations shall apply:
12.2 Bodies of nonagitating equipment shall be smooth,
watertight, metal containers equipped with gates that will
permit control of the discharge of the concrete. Covers shall be
provided for protection against the weather when required by
the purchaser.
12.3 The concrete shall be delivered to the site of the work
in a thoroughly mixed and uniform mass and discharged with
a satisfactory degree of uniformity as prescribed in Annex A1.
12.4 Slump tests of individual samples taken after discharge
of approximately 15 % and 85 % of the load will provide for a
quick check of the probable degree of uniformity (Note 14).
These two samples shall be obtained within an elapsed time of
not more than 15 min. If these slumps differ more than that
specified in Table A1.1, the nonagitating equipment shall not
be used unless the conditions are corrected as provided in 12.5.
12.5 If the requirements of Annex A1 are not met when the
nonagitating equipment is operated for the maximum time of
haul, and with the concrete mixed the minimum time, the
equipment shall only be used when operated using shorter
hauls, or longer mixing times, or combinations thereof that will
result in the requirements of Annex A1 being met.
13. Batch Ticket Information
13.1 The manufacturer of the concrete shall furnish to the
purchaser with each batch of concrete before unloading at the
site, a delivery ticket on which is printed, stamped, or written,
information concerning said concrete as follows:
13.1.1 Name of ready-mix company and batch plant, or
batch plant number,
13.1.2 Serial number of ticket,
13.1.3 Date,
13.1.4 Truck number,
13.1.5 Name of purchaser,
13.1.6 Specific designation of job (name and location),
Minimum Concrete Temperature as Placed
Section Size, in. [mm]
<12 [<300]
50 [10]
45 [7]
40 [5]
Temperature, min, °F [C]
55 [13]
7
C 94/C 94M – 04
statement that all tests performed by the laboratory or its agents
were in accordance with the applicable test methods or shall
note all known deviations from the prescribed procedures
(Note 17). The reports shall also list any part of the test
methods not performed by the laboratory.
13.1.7 Specific class or designation of the concrete in
conformance with that employed in job specifications,
13.1.8 Amount of concrete in cubic yards (or cubic metres),
13.1.9 Time loaded or of first mixing of cement and
aggregates, and
13.1.10 Water added by receiver of concrete and his initials.
13.2 Additional information for certification purposes as
designated by the purchaser and required by the job specifications shall be furnished when requested; such information as:
13.2.1 Reading of revolution counter at the first addition of
water,
13.2.2 Type, brand, and amount of cement,
13.2.3 Class, brand, and amount of coal fly ash, or raw or
calcined natural pozzolans,
13.2.4 Grade, brand, and amount of ground granulated
blast-furnace slag,
13.2.5 Type, brand, and amount of silica fume,
13.2.6 Type, brand, and amount of admixtures
13.2.7 Type, brand, and amount of fiber reinforcement,
13.2.8 Source and amount of each metered or weighed
water or recycled slurry,
13.2.9 Information necessary to calculate the total mixing
water. Total mixing water includes free water on aggregates,
batch water (metered or weighed) including ice batched at the
plant, wash water retained in the mixing drum, and water added
by the truck operator from the mixer tank,
13.2.10 Maximum size of aggregate,
13.2.11 Mass (amount) of fine and coarse aggregate,
13.2.12 Ingredients certified as being previously approved,
and
13.2.13 Signature or initials of producer’s representative.
NOTE 17—Deviation from standard test methods may adversely affect
test results.
NOTE 18—Deviation from standard moisture and temperature curing
conditions is often a reason for low strength test results. Such deviations
may invalidate the use of such test results as a basis for rejection of the
concrete.
16. Sampling and Testing Fresh Concrete
16.1 The contractor shall afford the inspector all reasonable
access and assistance, without charge, for the procurement of
samples of fresh concrete at time of placement to determine
conformance of it to this specification.
16.2 Tests of concrete required to determine compliance
with this specification shall be made by a certified ACI
Concrete Field Testing Technician, Grade I or equivalent.
Equivalent personnel certification programs shall include both
written and performance examinations as outlined in ACI
CP-1.
16.3 Samples of concrete shall be obtained in accordance
with Practice C 172, except when taken to determine uniformity of slump within any one batch or load of concrete (10.4,
11.3.3, 11.5.1, and 12.4).
16.4 Slump, air-content, density, and temperature tests shall
be made at the time of placement at the option of the inspector
as often as is necessary for control checks. In addition, these
tests shall be made when specified and always when strength
specimens are made.
16.5 Strength tests as well as slump, temperature, density,
and air content tests shall generally be made with a frequency
of not less than one test for each 150 yd3 (115 m3). Each test
shall be made from a separate batch. On each day concrete is
delivered, at least one strength test shall be made for each class
of concrete.
16.6 If preliminary checks of slump or air content are made,
a single sample shall be taken after the discharge of not less
than 1⁄4 yd3[1⁄4 m3]. All other requirements of Practice C 172
shall be retained. If the preliminary measurement of slump
(11.7) or air content (7.3) falls outside the specified limits,
address as indicated in section 16.6.1 or 16.6.2 as appropriate.
16.6.1 If the measured slump or air content, or both is
greater than the specified upper limit, a check test shall be
made immediately on a new test sample. In the event the check
test fails, the concrete shall be considered to have failed the
requirements of the specification.
16.6.2 If the measured slump or air content, or both is less
than the lower limit, permit adjustments in accordance with
11.7 or 7.3 or both, as appropriate, and obtain a new sample. If
the sample of the adjusted concrete fails, a check test shall be
made immediately on a new sample of the adjusted concrete. In
the event the check test fails, the concrete shall be considered
to have failed the requirements of the specification.
14. Plant Inspection
14.1 The manufacturer shall afford the inspector all reasonable access, without charge, for making necessary checks of
the production facilities and for securing necessary samples to
determine if the concrete is being produced in accordance with
this specification. All tests and inspection shall be so conducted
as not to interfere unnecessarily with the manufacture and
delivery of concrete.
15. Practices, Test Methods, and Reporting
15.1 Test ready-mixed concrete in accordance with the
following methods:
15.1.1 Compression Test Specimens—Practice C 31/C 31M,
using standard moist curing in accordance with the applicable
provisions of Practice C 31/C 31M.
15.1.2 Compression Tests—Test Method C 39/C 39M.
15.1.3 Yield, Mass per Cubic Foot—Test Method C 138/
C 138M.
15.1.4 Air Content—Test Method C 138/C 138M; Test
Method C 173/C 173M or Test Method C 231.
15.1.5 Slump—Test Method C 143/C 143M.
15.1.6 Sampling Fresh Concrete—Practice C 172.
15.1.7 Temperature—Test Method C 1064/C 1064M.
15.2 The testing laboratory performing acceptance tests of
concrete shall meet the requirements of Practice C 1077.
15.3 Laboratory reports of concrete test results used to
determine compliance with this specification shall include a
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C 94/C 94M – 04
17. Strength
17.1 When strength is used as a basis for acceptance of
concrete, standard specimens shall be made in accordance to
Practice C 31/C 31M. The specimens shall be cured under
standard moisture and temperature conditions in accordance
with the applicable provisions of Practice C 31/C 31M. The
technician performing the strength test shall be certified as an
ACI Concrete Strength Testing Technician, Concrete Laboratory Testing Technician—Grade II or by an equivalent written
and performance test program covering the relevant test
methods. If acceptance is based upon compressive strength test
results, the certification requirement is satisfied by certification
as an ACI Concrete Laboratory Testing Technician—Grade I or
by an equivalent written and performance test program.
17.2 For a strength test, at least two standard test specimens
shall be made from a composite sample secured as required in
Section 16. A test shall be the average of the strengths of the
specimens tested at the age specified in 4.2.1.1 or 4.4.1.1 (Note
19). If a specimen shows definite evidence other than low
strength, of improper sampling, molding, handling, curing, or
testing, it shall be discarded and the strength of the remaining
cylinder shall then be considered the test result.
tially higher than the specified strength. The amount higher depends upon
the standard deviation of the test results and the accuracy with which that
value can be estimated from prior data as explained in ACI 318 and
ACI 301. Pertinent data are given in Table 4.
18. Failure to Meet Strength Requirements
18.1 In the event that concrete tested in accordance with the
requirements of Section 17 fails to meet the strength requirements of this specification, the manufacturer of the readymixed concrete and the purchaser shall confer to determine
whether agreement can be reached as to what adjustment, if
any, shall be made. If an agreement on a mutually satisfactory
adjustment cannot be reached by the manufacturer and the
purchaser, a decision shall be made by a panel of three
qualified engineers, one of whom shall be designated by the
purchaser, one by the manufacturer, and the third chosen by
these two members of the panel. The question of responsibility
for the cost of such arbitration shall be determined by the
panel. Its decision shall be binding, except as modified by a
court decision.
19. Keywords
19.1 accuracy; blended hydraulic cement; certification;
ready-mixed concrete; scales; testing
NOTE 19—Additional tests may be made at other ages to obtain
information for determining form removal time or when a structure may
be put in service. Specimens for such tests are cured according to the
section on Field Curing in Practice C 31/C 31M.
TABLE 4 Overdesign Necessary to Meet Strength RequirementsA
17.3 The representative of the purchaser shall ascertain and
record the delivery-ticket number for the concrete and the exact
location in the work at which each load represented by a
strength test is deposited.
17.4 To conform to the requirements of this specification,
strength tests representing each class of concrete must meet the
following two requirements (Note 20):
17.4.1 The average of any three consecutive strength tests
shall be equal to, or greater than, the specified strength, f 8c, and
17.4.2 No individual strength test shall be more than 500 psi
[3.5 MPa] below the specified strength, f 8c.
Number of
TestsB
15
20
30 or more
300
466
434
402
15
20
30 or more
2.0
3.1
2.9
2.7
Standard Deviation, psi
400
500
600
622
851
1122
579
758
1010
526
665
898
Standard Deviation, MPa
3.0
4.0
5.0
4.7
7.3
10.0
4.3
6.6
9.1
4.0
5.8
8.2
Unknown
700
1392
1261
1131
C
C
C
Unknown
C
C
C
A
Add the tabulated amounts to the specified strength to obtain the required
average strengths.
B
Number of tests of a concrete mixture used to estimate the standard deviation
of a concrete production facility. The mixture used must have a strength within
1000 psi [7.0 MPa] of that specified and be made with similar materials. See
ACI 318.
C
If less than 15 prior tests are available, the overdesign should be 1000 psi [7.0
MPa] for specified strength less than 3000 psi [20 MPa], 1200 psi [8.5 MPa] for
specified strengths from 3000 to 5000 psi [20 to 35 MPa] and 1400 psi [10.0 MPa]
for specified strengths greater than 5000 psi [35 MPa].
NOTE 20—Due to variations in materials, operations, and testing, the
average strength necessary to meet these requirements will be substan-
ANNEX
(Mandatory Information)
A1. CONCRETE UNIFORMITY REQUIREMENTS
A1.1 The variation within a batch as provided in Table A1.1
shall be determined for each property listed as the difference
between the highest value and the lowest value obtained from
the different portions of the same batch. For this specification
the comparison will be between two samples, representing the
first and last portions of the batch being tested. Test results
conforming to the limits of five of the six tests listed in Table
A1.1 shall indicate uniform concrete within the limits of this
specification.
A1.2 Coarse Aggregate Content, using the washout test,
shall be computed from the following relations:
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C 94/C 94M – 04
TABLE A1.1 Requirements for Uniformity of Concrete
Requirement, Expressed as
Maximum Permissible Difference in
Results of Tests of Samples
Taken from Two Locations
in the Concrete Batch
Test
Mass per cubic foot [mass per cubic meter] calculated to an air-free basis, lb/ft3[kg/m3]
Air content, volume % of concrete
Slump:
If average slump is 4 in. [100 mm] or less, in. [mm]
If average slump is 4 to 6 in. [100 to 150 mm], in. [mm]
Coarse aggregate content, portion by mass of each sample retained on No. 4 [4.75-mm] sieve, %
Mass per unit volume of air-free mortarA based on average for all comparative samples tested, %.
Average compressive strength at 7 days for each sample,B based on average strength of all comparative test specimens, %
1.0 [16]
1.0
1.0 [25]
1.5 [40]
6.0
1.6
7.5C
A
“Test for Variability of Constituents in Concrete,” Designation 26, Bureau of Reclamation Concrete Manual, 7th Edition.4
Not less than 3 cylinders will be molded and tested from each of the samples.
C
Approval of the mixer shall be tentative, pending results of the 7-day compressive strength tests.
B
P 5 ~c/b! 3 100
SI units:
(A1.1)
where:
P = mass % of coarse aggregate in concrete,
c = saturated-surface-dry mass in lb [kg] of aggregate
retained on the No. 4 [4.75-mm] sieve, resulting from
washing all material finer than this sieve from the fresh
concrete, and
b = mass of sample of fresh concrete in mass per unit
volume container, lb [kg].
M5
b2c
V3A c
V 2 100 1 G
S
D
S
D
(A1.3)
where:
M = mass per unit volume of air-free mortar, lb/ft3 [kg/
m3],
b = mass of concrete sample in mass container, lb [kg],
c = saturated-surface-dry mass of aggregate retained on
No. 4 [4.75-mm] sieve, lb [kg],
V = volume of mass per unit volume container, ft3 [m3],
A = air content of concrete, %, measured in accordance
with 15.1.4 on the sample being tested, and
G = density of coarse aggregate (SSD).
A1.3 Mass per Unit Volume of Air Free Mortar shall be
calculated as follows:
Inch-pound units:
M5
b2c
V3A c
V 2 100 1 G
(A1.2)
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